Prevalence of serotype and multidrug-resistance of Streptococcus pneumoniae respiratory tract isolates in 265 adults and 36 children in Korea, 2002-2005.

In total, 301 isolates of Streptococcus pneumoniae collected from patients with respiratory tract infections admitted at primary clinics during 2002-2005 were tested for multidrug-resistance (MDR) phenotypes and their serotypes in Korea. The predominant serotypes were 19F, 19A, 23F, 11A, 3, 6A, and 6B, accounting for 67.8% of all isolates. Their serotype coverage by 23-valent polysaccharide vaccine and 7-valent conjugation vaccine was 73.1% and 39.2%, respectively. For the application of Clinical and Laboratory Standards Institute's new breakpoint for penicillin, the resistance rate of penicillin was 27.9% (but the penicillin resistance was 80.4% based on the previous breakpoint for penicillin of Clinical and Laboratory Standards Institute). Actually, the full resistance rate was only 4.0% (minimum inhibitory concentration >or=8 mg/L). Resistances to erythromycin, clindamycin, and tetracycline were very high (82.9%, 79.4%, and 71.7%, respectively). Especially, 56.1% of all the isolates were MDR, defined as resistant to three or more of the following agents: penicillin, erythromycin, clindamycin, cefotaxime, tetracycline, and levofloxacin. MDR strains were relatively associated with serotypes 19F, 19A, 23F, and 11A, accounting for 58.0% of the isolates. Their serotype coverage by 23-valent polysaccharide vaccine and 7-valent conjugation vaccine was 79.5% and 45.9%, respectively. Levofloxacin, as a representative fluoroquinolone, was active against 88.2% of all MDR isolates. Of particular concern was the high prevalence of MDR pneumococci in non-PCV7 serotypes with an MDR serotype 19A, 11A, 3, and 6A being mostly responsible. It would be prudent to consider more efficient protective strategies for people at high risk for pneumococcal diseases in regions with a high prevalence of MDR pneumococci.